{"id":23487,"date":"2021-09-16T00:00:00","date_gmt":"2021-09-16T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=23487"},"modified":"2021-10-22T11:46:19","modified_gmt":"2021-10-22T11:46:19","slug":"apy-masterclass-how-to-enrich-a-nebulas-colours","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2021\/09\/16\/apy-masterclass-how-to-enrich-a-nebulas-colours\/","title":{"rendered":"APY Masterclass: How to enrich a nebula\u2019s colours"},"content":{"rendered":"\n

Use editing software to bring out hydrogen-alpha colours in Orion<\/p>\n\n

<\/div>
\n

Astronomy Photographer of the Year<\/strong><\/p>\n\n\n\n

Advice from a shortlisted entrant in the \u2018Skyscapes\u2019 category<\/p>\n<\/div><\/section>\n\n

\"\"
Paul\u2019s \u2018Questions\u2019 image combines a stunning mountain foreground in Canterbury Hill Country, New Zealand, with the rich, colourful detail of Orion ALL PICTURES: PAUL WILSON<\/figcaption><\/figure><\/div>\n\n

My \u2018Questions\u2019 image was shortlisted in the \u2018Skyscapes\u2019 category at the Astronomy Photography of the Year competition in 2020. I created it after deciding to take an image linking our planet to the sky, but without featuring the usual Milky Way core. I started by shooting a mountain panorama during the Blue Hour \u2013 when the last remaining sunlight casts a blue glow into the dusk \u2013 to get maximum detail, and then set up my gear and waited for darkness and the Orion Molecular Cloud Complex.<\/p>\n\n

I used a hydrogen-alpha modified Canon EOS 6D camera with a 40mm Sigma Art lens at f\/2, mounted on a Star Adventurer mount and took 38 frames, using exposures of 90 seconds at ISO 800.<\/p>\n\n

I processed the image using a Luminance, Red, Green and Blue (LRGB) editing technique in Lightroom and Photoshop to bring out the hydrogen-alpha colours from the emission nebula. My friend and fellow astrophotographer Ian Norman showed me the technique and I\u2019m going to explain how it works here. It involves stacking multiple shots to reduce noise (unwanted artefacts), creating a high-contrast \u2018Luminance\u2019 layer and then overlaying it with a \u2018Colour\u2019 layer to produce an image that reveals the data hidden in the RAW image files.<\/p>\n\n

To begin the process select the RAW images (like I did of Orion) and import them into Lightroom. Next, click the \u2018Develop\u2019 module in the top menu and scroll down from the displayed \u2018Basic\u2019 panel (on the righthand side) to find the \u2018Noise Reduction\u2019 panel and set all the fields to 0. Scroll back up to the \u2018Basic\u2019 panel and set a neutral white balance by increasing \u2018Vibrance\u2019 and \u2018Saturation\u2019 values in the \u2018Presence\u2019 section to +100. Then, in the \u2018WB\u2019 (white balance) section of the \u2018Basic\u2019 panel, find an even balance between the colour sliders (Screenshot 1), before resetting \u2018Vibrance\u2019 and \u2018Saturation\u2019 to 0.<\/span><\/p>\n\n

\"\"
Screenshot 1: In the \u2018White Balance\u2019 section of the \u2018Basic Panel\u2019, you can find an even balance between the colour sliders<\/figcaption><\/figure><\/div>\n\n

Create a panorama<\/strong><\/h4>\n\n

Next, press \u2018Ctrl+A\u2019 to select all the images and click \u2018Sync\u2019 at the bottom of the \u2018Develop\u2019 module, which brings up the \u2018Synchronize Settings\u2019 box. Here click \u2018Check All\u2019 on the bottom left and then click \u2018Synchronize\u2019 on the bottom right. Now use the mouse to right-click on the selected images and select \u2018Edit in > Merge to panorama in Photoshop\u2019. This launches Photoshop and loads the panorama window. In the \u2018Photomerge\u2019 option box untick \u2018Blend Images Together\u2019 and click \u2018OK\u2019. Next, select all the images that Photoshop has opened in \u2018Layers\u2019, by right-clicking the mouse and selecting \u2018Convert to Smart Object\u2019. In the top bar open the \u2018Layer\u2019 drop-down menu and click \u2018Smart Objects > Stack Mode > Median\u2019. Right-click the image and select \u2018Flatten Image\u2019 to reduce noise.<\/span><\/p>\n\n

Now that we have a \u2018Colour\u2019 layer we can create a high-contrast \u2018Luminance\u2019 layer. Use the mouse to right-click the \u2018Colour\u2019 layer and select \u2018Convert to Smart Object\u2019. Next, press \u2018CTRL+J\u2019 a couple of times to replicate the layer, making three. Rename the two new layers as \u2018Nebulosity\u2019 and \u2018Detail\u2019 and then hide them by clicking the eye icon to the left of the \u2018Layers\u2019 tab.<\/span><\/p>\n\n

The next step is to remove the stars in the \u2018Colour\u2019 layer. Select it and then go to the top bar and open the \u2018Filter\u2019 drop-down menu and click \u2018Noise > Dust & Scratches\u2019. In the \u2018Dust & Scratches\u2019 box set the \u2018Radius\u2019 to 8 (Pixels) and the \u2018Threshold\u2019 to 15 (Levels), as increasing the \u2018Threshold\u2019 will bring back detail. Doing this will eliminate all but the brightest stars. <\/span>Smooth this layer by opening the \u2018Filter\u2019 drop-down menu again, and click \u2018Blur\u2019 > \u2018Gaussian Blur\u2019 and set the \u2018Radius\u2019 to 3 (Pixels) in the \u2018Gaussian Blur\u2019 box.<\/p>\n\n

\"\"
Screenshot 2: Adjust the colour sliders in the \u2018Black & White Properties\u2019 box to bring out contrast; an increase in \u2018Magenta\u2019 will enhance hydrogen-alpha<\/figcaption><\/figure><\/div>\n\n
\"\"
Screenshot 3: Make adjustments to \u2018Curves\u2019 levels in the \u2018Nebulosity\u2019 layer<\/figcaption><\/figure><\/div>\n\n

We now need to adjust the \u2018Detail\u2019 layer. Select and unhide this layer by clicking on the eye icon in the \u2018Layers\u2019 tab, then find the \u2018Black & White\u2019 icon in the \u2018Adjustments\u2019 panel above the \u2018Layers\u2019 tab and click it. Adjust each of the colour sliders in the \u2018Black & White Properties\u2019 box (see Screenshot 2) to bring out contrast \u2013 for example, increasing \u2018Magenta\u2018 will reveal the hydrogen-alpha in your image. Next, click the \u2018Curves\u2019 icon in the \u2018Adjustments\u2019 panel and add contrast to your image with this tool. Under the \u2018Layers\u2019 tab, select \u2018Curves\u2019, \u2018Black & White\u2019 and \u2018Detail\u2019 and right-click the mouse on \u2018Smart Object\u2019. <\/span>Rename the adjusted layer as \u2018Detail\u2019.<\/p>\n\n

For the \u2018Nebulosity\u2019 layer, repeat the steps from the \u2018Colour\u2019 and \u2018Detail\u2019 layer (see Screenshot 3). Under \u2018Layers\u2019, select \u2018Curves\u2019, \u2018Black & White\u2019 and \u2018Nebulosity\u2019 and right-click on \u2018Smart Object\u2019. <\/span>Rename the layer as \u2018Nebulosity\u2019.<\/p>\n\n

Next, we combine the \u2018Detail\u2019 and \u2018Nebulosity\u2019 layers with an inverted layer mask. To do this, hide the \u2018Nebulosity\u2019 layer and select the \u2018Detail\u2019 layer. Press \u2018CTRL+A\u2019 to select the main image preview shown on the screen. Use \u2018CTRL+C\u2019 to copy it, and then re-enable the \u2018Nebulosity\u2019 layer and add a layer mask by clicking \u2018Add vector mask\u2019 at the bottom of the \u2018Layers\u2019 tab. Paste the copied contents into the new mask on our \u2018Nebulosity\u2019 layer. Hold \u2018ALT\u2019 and click on the mask, before pressing \u2018CTRL+V\u2019 to paste and then \u2018CTRL+I\u2019 to invert the contents. Group the \u2018Nebulosity\u2019 and \u2018Detail\u2019 layers by selecting both, then press \u2018CTRL+G\u2019 and set the group blend mode to \u2018Luminosity\u2019 \u2013 this creates our \u2018Luminance\u2019 layer. Now select the \u2018Colour\u2019 layer and click the \u2018Vibrance\u2019 and \u2018Hue\/Saturation\u2019 icons in the \u2018Adjustments\u2019 panel to make increases. We can now combine our layers by right-clicking and selecting \u2018Flatten Image\u2019.<\/span><\/p>\n\n

Finally, the mountain can be added by opening the image of it and using Photoshop\u2019s \u2018Magic Wand Tool\u2019 to select the foreground. We apply a layer mask where the sky is black and the ground is white to create our final image (see the main \u2018Questions\u2019 image, opposite).<\/p>\n\n

<\/div>
\n

3 QUICK TIPS<\/h4>\n\n\n\n

1. <\/strong>The number values for this image may not fit your data, so alter them as necessary.<\/p>\n\n\n\n

2. <\/strong>The key aim of LRGB processing is to enhance the hydrogen-alpha nebulosity in the image.<\/p>\n\n\n\n

3. <\/strong>Be careful, as increasing the \u2018Black & White\u2019 luminosity too much may lead to data being lost.<\/p>\n<\/div><\/section>\n\n

\n
\n
\"\"<\/figure><\/div>\n<\/div>\n\n\n\n
\n

Paul Wilson is an astrophotographer based in Christchurch, New Zealand. He was shortlisted in <\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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